Physical development
Human development is the process of growing to maturity and reaching one's full potential. In biological terms, this entails growth from a one-celled zygote to an adult human being. The psychological study of human development is called developmental psychology. We can conceive of human development in a variety of ways. In political-economic terms, human development has to do with stability, security and relative prosperity. In social terms, it has to do with literacy, education, social relationships, quality of life, etc. In moral terms, it has to do with the development of the conscience, moral awareness, and the will and capacity to act according to our knowledge of what is right. In psychological terms, human development has to do with mental health, self-esteem, success in significant relationships, happiness Biological development Development begins with fertilization, the process by which the male gamete, the sperm cell, and the female gamete, the oocyte, fuse to give rise to a diploid cell, the zygote. In medicine, pregnancy is defined as beginning when a fertilized zygote becomes implanted in a woman's uterus. This occurs when the zygote then becomes embedded into the endometrium (lining of the uterus) where it forms a placenta, for the purpose of receiving essential nutrients through the uterus wall. The umbilical cord in a newborn child signifies the remnants of implantation. The zygote undergoes rapid mitotic divisions with no significant growth (a process known as cleavage) and cellular differentiation, leading to development of an embryo. Childbirth is the process in which the baby is born. It is considered by many to be the beginning of a person's life, where age is defined relative to this event in most cultures. Developmental stages Terms for developmental age groups include, with their approximate age ranges: * Prenatal development ** Zygote, the point of Conception, fertilization ** blastocyst the period between conception and embryonic stages ** Embryo; the embryonic period starts at three weeks and continues until the end of the 8th week of pregnancy ** Embryogenesis ** fetus; the fetal stage begins at the end of the 8th week and continues until childbirth ** Birth * Neonatal development * Early childhood development ** Infant development (baby, newborn) (0-1) ** Toddler (1-2) ** Play age (3-5) * Childhood development *** Early Childhood (5-7) *** Middle Childhood (7-9) *** Preadolescence (preteen) (9-13) * Adolescent development and puberty (teenage) (14-18) * Adult (18-older) ** Early adulthood (18-22) ** Middle age (22-64) ** Advanced adult/Senior citizen (65+) * Death (occurs at various ages, depending on person) Physical development milestones * Ability to lift and control the orientation of the head * Crawling begins * Walking begins * Speech begins * Voice lowers in pitch (especially noticeable in boys) * Pubic hair appears * Genitals and reproductive organs mature * Menses begin (females) * Body hair and facial hair appears Note: the Tanner stages can be used to approximately judge a child's age based on physical development. Further aspects of development linked to physical development *Motor development *Perceptual development *Perceptual motor development *Psychomotor development *Psychosexual development *Sexual development Assessment *Tanner stages ----- See also * Age differences * Aging (attitudes toward) * Animal development * Auxology * Cognitive development * Delayed development * Developmental biology * Evolutionary developmental psychology * Evolutionary developmental psychopathology * Human development * Life history theory * Mammalian embryogenesis * Neural development * Physical maturity * Precocious development * Psychogenesis * Sex linked developmental differences References & Bibliography Key texts Books Papers Additional material Books Papers External links Category:Human development Development Category:Developmental psychology Category:Physical development